PLAP expression, often at high levels, has been described to occur in up to 100% of testicular germ cell neoplasia in situ [20, 28, 30], up to 100% of seminoma [4, 6, 7, 9, 20, 21, 22, 23, 30, 35, 36, 38, 41, 42], up to 100% of embryonal carcinoma [35, 42], up to 87% of yolk sac tumors [30], and up to 100% of choriocarcinomas [12, 16, 19]. The gene discussed is ALPP; the disease is seminoma.